Production of trialkylboranes



United States Patent PRODUCTION OF TRIALKYLBORANES John C. Perrine, Jr., Pasadena, Calif., assignor'to Olin Mathieson Chemical Corporation, a corporation of Virginia No Drawing. Application July 29, 1957 Serial No. 675,517

4 Claims. (Cl. 260-6065) This invention relates to a method for the production of trialkylboranes of the type RR'R"B wherein R, R and R are lower alkyl radicals, particularly those containing from 1 to 4 carbon atoms. As is described in U. S. Patent No. 2,266,776, to Leum, such trialkylboranes, in the form of amine addition products, are useful additives to diesel fuels and the like for the purpose of increasing their cetane number. In addition, such trialkylboranes are useful for the purpose described in Klein, Nadeau, Schoen and Bliss application Serial No. 614,768, filed October 8, 1956.

In accordance with the present invention, the trialkylboranes are produced by reacting boric oxide (B 0 and a compound of the class RAlXX' wherein R is an alkyl radical containing from'l to 4 carbon atoms, and X and X are alkyl radicals containing from 1 to 4 carbon atoms or are halogen atoms, particularly iodine, bromine or chlorine. Thus, RAlXX can be a trialkyl aluminum compound, such as aluminum trimethyl or aluminum triethyl, or it can be an alkyl aluminum halide, such as methyl aluminum di-iodide or dimethyl aluminum monoiodide. X and X, when alkyl, can be the same as R or, if desired, R, X and X can even all be different. In carrying out the reaction, the relative proportions of bon'c oxide and RAlXX can be varied widely. Preferably, however, the ratio of the number of alkyl radicals introduced into the reaction zone in the RAlXX to the number of boron atoms introduced into the reaction zone in the boric oxide is within the range from about 0.75 to 12. In other words, the amount of RAlXX' employed can be from one-fourth to four times that stoichiometrically required to convert the boron in the boric oxide to a trialkylborane. The reaction between the boric oxide and RAlXX is generally carried out at a temperature within the range from about 50 C. to 200 C., although somewhat higher and somewhat lower reaction temperatures can also be used. After the reaction has been carried out to produce the trialkyl borane,

the desired product can be separated from the reaction mixture using conventionalmeans, particularly by precise fractionation of the reaction mixture.

The following examples illustrate various embodiments which fall within the scope of this invention.

4. The method of claim 1 aluminum,

Patented Sept. 23, 1958 Example I 5 grams of dry boric oxide was placed in a tube having a capacity of about 50 ml. fitted with a stopcock. The tube was cooled to 196 C. by immersion in a liquid nitrogen bath and was evacuated. 2 cc. of aluminum trimethyl was condensed into the cooled tube. The stopcock was closed and the tube was allowed to warm to room temperature. Following this, the tube was gently heated for four hours at C. During this time, the aluminum trimethyl was refluxed off of the both: oxide. At the end of this time, the reaction tube was immersed in a Dry Ice-acetone bath at 78 C. An infrared spectrum of the material that was volatile at -78 C. was identical with the spectrum of pure trimethyl borane. The yield of the trimethylborane was Example II Dry boric oxide, 5 grams, was placed in a 35 cc. three necked flask fitted with a pressurized addition funnel, reflux condenser, and stopper. Aluminum methyl iodide, (composed of approximately equal amounts by weight of CH AlI and (CH AlI), 5 cc., was placed in the addition funnel. The top of the reflux condenser was connected to a vacuum source through a trap immersed in liquid nitrogen. The flask was then immersed in liquid nitrogen and evacuated. After evacuation the liquid nitrogen bath was removed from the flask and the aluminum methyl iodide was added to and refluxed from the boric oxide for four hours. At the end of this time the trap was immersed in a bath cooled to 78 C. The infrared spectrum of the material volatile at 78 C. was identical to one of pure trimethylborane. The yield of trimethylborane was 50 mg.

What is claimed is:

1. A method for the production of a trialkyl borane which comprises reacting boric oxide and a compound of the class RADQC at a temperature within the range from about 50 C. to about 200 C., R being an alkyl radical containing from- 1 to 4 carbon atoms, X being selected from the group consisting of halogen atoms and alkyl radicals containing from 1 to 4 carbon atoms, X being selected from the group consisting of halogen atoms and alkyl radicals containing from 1 to 4 carbon atoms, and the ratio of the number of alkyl radicals introduced into the reaction zone in the RAlXX' to the number of boron atoms introduced into the reaction zone in the boric oxide being within the range from 0.75 to 12.

2. The method of claim 1 wherein X and X are alkyl radicals.

3. The method of claim 1 wherein X'and X are iodine. wherein RAlXX is trimethyl No references cited. 

1. A METHOD FOR THE PRODUCTION OF A TRIALKYL BORANE WHICH COMPRISES REACTING BORIC OXIDE AND A COMPOUND OF THE CLASS RAIXX'' AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 50*C. TO ABOUT 200*C., R BEING AN ALKYL RADICAL CONTAINING FROM 1 TO 4 CARBON ATOMS X BEING SELECTED FROM THE GROUP CONSISTING OF HALOGEN ATOMS AND ALKYL RADICALS CONTIANING FROM 1 TO 4 CARBON ATOMS, X'' BEING SELECTED FROM THE GROUP CONSISTING OF HALOGEN ATOMS AND ALKYL RADICALS CONTAINING FROM 1 TO 4 CARBON ATOMS, AND THE RATIO OF THE NUMBER OD ALKYL RADICALS INTRODUCED INTO THE REACTION ZONE ON THE RAIXX'' TO THE NUMBER OF THE BORON ATOMS INTRODUCED INTO THE REACTION ZONE IN THE BORIC OXIDE BEING WITHIN THE RANGE FROM 0.75 TO
 12. 